Synthetic resin container having a craze pattern thereon and method for producing the same

ABSTRACT

A synthetic resin container according to the invention has a craze pattern on the outer surface of its body. The container comprises an inner layer that comes into direct contact with content during its storage, an outer layer laid over the inner layer, and a translucent protective layer laid over the outer layer. The outer layer carries a craze pattern that has been obtained by applying a solvent to a preform or parison of the container after blow molding thereof. The protective layer covers and protects that portion of the outer layer, which carries the craze pattern, and preserves its visibility from outside.

BACKGROUND OF THE INVENTION

[0001] The present invention relates to a synthetic resin containerhaving a unique appearance and a method for producing the same.

[0002] Usually, a synthetic resin container is decorated by applying alabel or printing a pattern on its surface. In recent years, trials havebeen made to produce a craze pattern on a synthetic resin container asin a glass container, to give a high-grade appearance to the container.However, up to the present, there has not been known any technology thatallows one to readily and securely produce such a synthetic resincontainer having a decorative craze pattern thereon.

SUMMARY OF THE INVENTION

[0003] It is an object of the present invention to provide a syntheticresin container having a craze pattern on its outer surface, and topropose a method for producing such a container.

[0004] To this end, the present invention provides a synthetic resincontainer having a craze pattern on an outer surface of a containerbody, which comprises, in terms of its wall profile, an inner layer thatcomes into direct contact with content during storage thereof, an outerlayer laid over the inner layer and having a craze pattern that has beenformed by applying a solvent on a blow molded container body, and atranslucent protective film covering, from outside, at least part of theouter layer that carries the craze pattern.

[0005] In the synthetic resin container according to the presentinvention, it is preferred that the outer layer is comprised of a cyclicpolyolefin resin, and the inner layer is comprised of an olefin-basedresin, such as polyethylene resin, poly-propylene resin or the like, orof a polyester resin, such as polyethylene telephthalate or the like.

[0006] Further, in the synthetic resin container according to thepresent invention, it is preferred that the inner layer is colored,while the outer layer and protective film are made of a transparent orsemi-transparent material.

[0007] The present invention further provides a method for producing asynthetic resin container having a craze pattern on an outer surface ofa container body, which comprises the steps of preparing a preform orparison having a wall that comprises at least two layers wherein aninner layer and an outer layer are laid over one another by an extrusionmolding or injection molding, subjecting the preform or parison to ablow molding, applying a solvent on the surface of a molded bodyobtained by the blow molding, thereby causing cracks to develop there asa craze pattern, and forming a translucent protective film on the outersurface of the molded body so that the film covers the craze pattern.

[0008] In preparing the preform or parison according to theabove-mentioned method, it is preferred that the outer layer is madefrom a cyclic polyolefin resin, and the inner layer is made from apolyolefin-based resin such as polyethylene resin, polypropylene resinor the like, or from a polyester resin such as polyethylenetelephthalate or the like.

[0009] The solvent to be applied on the outer layer to cause cracks todevelop there in a craze pattern preferably comprises n-heptane.

BRIEF DESCRIPTION OF THE DRAWINGS

[0010] The present invention will be described in detail hereinafter,with reference to preferred embodiments illustrated in the accompanyingdrawings.

[0011]FIGS. 1a and 1 b are, respectively, front view and side view of asynthetic resin container according to the present invention, while FIG.1c is an enlarged sectional view of its wall region R.

[0012]FIG. 2 is a sectional view showing one example of a preformsuitable for producing a container according to the present invention.

[0013]FIG. 3 is a sectional view showing another example of a preformalso suitable for producing a container according to the presentinvention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0014] In FIGS. 1a, 1 b and 1 c, reference numeral 10 represents asynthetic resin container according to the present invention. Generally,the synthetic resin container 10 exhibits a bottle shaped and has acraze pattern 12 a on the outer surface of the container body as aresult of minute cracks developed there. As shown in FIG. 1c, the wallof the container body has a layered structure comprising at least threelayers obtained by sequentially overlapping the following layers in thestated order: an inner layer 11, an outer layer 12 carrying the crazepattern 12 a, and a translucent protective layer 13 covering that partof the outer layer 12, which carries the craze pattern 12 a.

[0015] In order to prepare a synthetic resin container having astructure as described above, first of all, a preform 20 is prepared byan injection molding or extrusion molding to have a wall comprising twolayers as shown in FIG. 2, with an inner layer 21 corresponding with theinner layer 11 of the container 10 being made from a polyolefin-basedresin, such as polyethylene resin, polypropylene resin or the like, or apolyester resin, such as polyethylene telephthalate or the like, andwith an outer layer 22 corresponding with the outer layer 12 of thecontainer 10 being made from a cyclic polyolefin resin.

[0016] Upon preparation of the preform 20, it is possible to carry outco-injection molding or co-extrusion molding so as to form the inner andouter layers 21, 22 simultaneously. Alternatively, the inner and outerlayers 21, 22 may be formed, respectively, by injection molding orextrusion molding as separate bodies, and these bodies may be integratedwith each other by a subsequent step. Still alternatively, a preform ofone of the inner and outer layers 21, 22 may be formed by injectionmolding or extrusion molding, and so-obtained preform may be used as aninsert upon injection of the material for the other of the inner andouter layers 21, 22 so as to complete the preform 20.

[0017] The preform 20 is then subjected to a bi-axial stretch blowmolding, to obtain a molded body having a desired shape. A solvent isapplied on the outer surface (outer layer 12) of the molded body tocause cracks to develop as a craze pattern 12 a. Subsequently, over theentire outer surface of the molded body, a shrink label is bonded or acoating material is applied (by spraying or coating) to form aprotective film there, which prevents separation of the outer layer. Theprotective film 13 is made transparent or semitransparent so as topreserve the visibility of the crazing pattern 12 a from outside.

[0018] Variations of the above-mentioned method which are otherwisesimilar except that the preform 20 is substituted for a parison, and thebiaxial stretch blow molding for direct blow molding are also includedin the present invention, though they are not illustrated here. Thecontainer according to the present invention may take, in addition to abottle shape illustrated in the figure, a tubular shape which is formedby subjecting the compound material to co-extrusion molding withoutresorting to blow molding to thereby produce a tubular body. The tubularbody may be integrated in molding with a head, or combined with a headseparately prepared, and then have its bottom sealed.

[0019] The cyclic polyolefin resin preferably comprises, for example,addition polymers of cyclic olefin and áolefin, or hydrates ofring-opened polymers of cyclic olefin. The addition polymer of cyclicolefin and áolefin which contains cyclic olefin at a concentration of5-60 mol % may comprise, for example, “Apl”® (Mitsui Chemicals Co.) and“Zeoner”® (Zeon Corp.). Although the polyolefin-based addition polymercontaining a cyclic olefin component is a copolymer that comprises, asits essential components, a cyclic olefin component and anethylene-based component in addition to those components, the polymer inquestion may further comprise an unsaturated monomer component which canco-polymerize with said polyolefins. Such copolymerizable unsaturatedmonomers may comprise cyclic diene compounds, such as dicyclopentadiene.

[0020] A preferred coating material suitable for the coating maycomprise two-liquid type urethane-based coating materials, though thecoating material suitable for the present invention is not limitedthereto. Namely, there may be adopted coating materials generally usedfor coating applications, and there is no specific limitation in termsof the coating method.

[0021] The cyclic polyolefin resin acts very effectively as a barrieragainst invasion of moisture, and is suitably applied as a coatingmaterial to protect, when used as a coating of a container, its content.However, it is susceptible to strains and to invasion of vegetable ormineral oils or greases. Thus, when a container is coated with a cyclicpolyolefin resin based coating material, and particularly when its wallcarries residual strains, handling the container with fingertips tendsto leave grease on its surface that may lead to development of cracks onits surface. The present invention is a deliberate exploitation of thisphenomenon, and aims at decorating a container by deliberatelygenerating minor cracks on its surface. Deliberate generation of minorcracks on the surface of a container can be achieved by applyingn-heptane on the surface of a molded body produced by blow molding.

[0022] In the synthetic resin container 10 according to the presentinvention, the inner layer 11, outer layer 12 and protective film 13constituting its wall may be made transparent or semi-transparent,though they may be given any desired color as appropriate. Particularly,in case the inner layer 11 is colored while the outer layer 12 andprotective film 13 are made transparent or semi-transparent, thecontainer exhibits a deep tone color when observed from outside. Thepreform or parison 20 used in the present invention may be prepared sothat the outer layer 22 covers and surrounds the inner layer 21 only atthe container body portion, as shown in FIG. 3. The relation of theouter layer to the inner layer is not limited to any specificarrangement.

[0023] It will be appreciated from the foregoing description that,according to the present invention, it is possible to efficientlyproduce a synthetic resin container having a desired craze pattern onits surface by only carrying out simple process steps. Moreover,according to the present invention, the container has a protective filmsuch as a shrink label or coating applied over the craze pattern in theouter layer. Thus, even if the container is contaminated on its surfacewith vegetable or mineral oil or greases, development of further cracksis positively prevented, without influencing over the function of thecontainer.

[0024] The present invention has been described with reference topreferred embodiments. However, it is of course that various embodimentsother than those described above are possible without departing thescope of the invention.

1. A synthetic resin container having a craze pattern on an outersurface of a container body, said container comprising: an inner layerthat comes into direct contact with content during its storage; an outerlayer carrying a craze pattern which has been formed by applying asolvent to the container body after a blow molding thereof; and atranslucent protective layer covering from outside at least part of theouter layer carrying the craze pattern.
 2. The synthetic resin containeraccording to claim 1, wherein the outer layer is comprised of a cyclicpolyolefin resin, and the inner layer is comprised of an olefin-basedresin, such as a polyethylene resin or polypropylene resin or the like,or of a polyester resin, such as polyethylene telephthalate or the like.3. The synthetic resin container according to claim 1, wherein the innerlayer is applied with a color, and the outer layer is transparent orsemi-transparent.
 4. A method for producing a synthetic resin containerhaving a craze pattern on an outer surface of a container body, saidmethod comprising the steps of: preparing a preform or parison having awall that comprises at least two layers wherein inner and outer layersare laid over one another by an extrusion molding or injection molding;subjecting the preform or parison to a blow molding and subsequentlyapplying a solvent on the outer surface of the molded body, therebycausing cracks to develop there as a craze pattern; and forming atranslucent protective layer on the outer surface of the molded body soas to cover the craze pattern.
 5. The method for producing a syntheticresin container according to claim 4, wherein the outer layer iscomprised of a cyclic polyolefin resin, and the inner layer is comprisedof an olefin resin, such as a polyethylene resin or polypropylene resinor the like, or of a polyester resin, such as polyethylene telephthalateor the like.
 6. The method for producing a synthetic resin containeraccording to claim 4, wherein n-heptane is applied as said solvent, forcausing cracks to develop on the surface of the molded body as a crazepattern.